In my copending patent application 07/296,871 filed Jan. 12, 1989 as a continuation of my now abandoned patent application 07/115,008 filed Oct. 28, 1987 I describe a cylindrical cutter head comprising a cutter head body having a cylindrical surface which is centered on an axis and which is formed with a plurality of radially outwardly open grooves extending parallel to the axis and narrowing toward the surface of the cutter head body. A disposable knife blade clamped in each of the main grooves has an axially extending formation and a centrifugal wedge positioned in each of the main grooves clamps the knife blade. A one-piece holding bracket interposed between the knife blade and the centrifugal wedge has a pair of unitary but relatively elastically displaceable parts one of which is engageable with the blade and in turn has an axially extending formation complementary to and interfitting with the formation of the blade. The other part of the bracket is fixed to the cutter head body and the bracket is elastically deformable for displacement of its one part between a normal position spaced slightly from the blade and permitting axial insertion and release of the knife blade and a holding position bearing on the blade and pressing same against the side of the main groove. The wedge is angled and positioned such that on rotation of the body it is urged centrifugally outward and presses the one part of the bracket into the holding position.
Furthermore in my prior-art system the holding bracket is constituted by a single L-cross-section profile having one leg forming the one part and another leg forming the other part. Screws attach the base strip to the floor of the main groove. This main groove has a stepped floor with a lower level to which the one leg of the bracket is screwed and which extends all the way to the trailing main-groove flank, and an upper level extending from the leading edge of the lower level to the leading flank of the groove. Both of these levels are formed as surfaces substantially perpendicular to the surfaces they terminate at, that is the trailing lower level is perpendicular to the trailing flank and the leading upper level to the leading flank.
Such a system is extremely simple and can, therefore, be built at very low cost while being easy to use. It nonetheless has the disadvantage that it is intended for use only with relatively narrow single-use blades, that is blades with a single cutting edge that cannot normally be reground and reused. Unfortunately many applications where the blade is subject to considerable wear or is likely to strike foreign objects necessitate the use of relatively wide double-edge or regrindable blades.
Accordingly a blade assembly such as described in DE-Z Holztechnik (35th year, 1955, volume 9, pages 411ff) where the cutter body, which is centered on and rotated about an axis, has a pair of diametrically opposite slots. Each slot has, relative to the normal direction of rotation of the cutter body, a leading flank which extends substantially radially of the blade axis and a trailing flank which forms an acute angle with a radius of the blade axis and which converges radially outward with the leading flank. The main groove further has a floor or base surface that extends perpendicular to the leading flank, that is tangent at the leading flank to an imaginary cylinder centered on the cutter-body axis. Formed in this main groove is a secondary groove having a trailing flank that is a coplanar extension of the main groove's trailing flank. This secondary groove or groove extension allows one to use standard wide blades that can be ground down and then reinstalled for many uses. Such a blade lies on the inclined trailing wall of the main groove and projects with its blunt back edge radially inward into the groove extension. Between the blade and the leading flank there is a wedge-section clamping bar which is braced with screws against the leading flank. Such an arrangement does allow a regrindable blade to be used, but is somewhat complex. It does not, however, allow narrow single-use or reversible blades to be employed.